1. Field of the Invention
The present invention relates to a coating device, and more particularly to an on-machine coater that constitutes a coating device in which the coater and the paper machine are integrated.
2. Description of the Related Art
The production of coated paper such as the printing paper used for catalogues and the like along with pressure-sensitive paper and heat-sensitive paper is based on the coating of application medium, for example paint, using a coater on a web (base material) which serves as the base paper, and the drying therof. Machines that coat application medium, for example paint, in this way are generically referred to as coaters. Commonly employed coaters include blade coaters, rod coaters and air-knife coaters that utilize a post-metering method in which, following the excess coating of application medium, for example paint, on the web, the application medium, for example paint, is either scraped off using a blade or small-diameter rod or blown off using an air-knife and measured (metered).
On the other hand, paper machines, which constitute the machines used to manufacture printing paper and coated base paper or the like, include a head box used to uptake a slurry which constitutes a suspension of pulp or the like and apply it out through a tip-end nozzle, a wire part used to dewater the slurry from the head box to form a paper layer (web), a press part used to pick up and dewater the web from the wire part, and a large number of cylinders that are heated by steam, as well as a dryer part in which the web from the press part is pushed against these cylinders to afford the drying thereof, a large number of vertically-stacked cast iron rollers, a calender for smoothing the web from the dryer part, and a reel around which the web from the calender is wound.
The formation of the paper produced by a paper machine into a coated paper normally involves the use of an on-machine coater. That is to say, the paper roll wound around the reel of the paper machine is mounted on an unwinder of the on-machine coater, and the web pulled from the unwinder is coated by way of a coater. The web coated by the coater is dried by both a non-contact dryer and a cylinder dryer and wound around a reel. Gloss is imparted to the web wound around the reel by way of a supercalender.
Although paper manufacture and coating are normally performed using separate machines, devices in which the paper machine and coater are integrated and from which the reel of the paper machine and the unwinder of the coater are omitted, which are generically referred to as on-machine coaters, are sometimes employed.
FIG. 1 of the drawings is a front view of one example of an on-machine coater. The symbol 1 in the diagram denotes a dryer part (dryer cylinder) provided in the final stage of a paper machine. The symbol 2 denotes a smoothing press (calender) used to smooth a web A, and the symbol 3 denotes a size press. Although the size press, which is normally arranged along the dryer part of the paper machine, is predominantly used for the coating of starch or the like on the web to improve the printability of the paper, it is sometimes arranged in the on-machine coater and used for the coating of a pigment application medium, for example paint, of clay or the like.
FIGS. 2A and 2B show front views of a size press arranged in the on-machine coater disclosed by “Technology Annual Machines•Materials•Pharmaceuticals Conspectus 2006”, Pulp and Paper Technology Times, Published 1 Sep. 2005, Vol. 48 No. 9, pages 128-129. When the size press is used for the coating of a pigment application medium, for example paint, the coated amount is 5 to 10 g/m2 per surface, the speed is 1000 to 2000 m/min, and the nip pressure is 30 to 60 kg/cm. FIG. 2A illustrates coating being simultaneously performed on the two surfaces of the web A, and FIG. 2B illustrates the separate implementation of coating on the two surfaces of the web A. Although, when the size press of a paper machine is used for the coating of starch or the like on the web, a starch pond, through which the web is passed therethrough and coated therewith, is formed on the upper part of the nip, when the size press is used for the coating of a pigment application medium, for example paint, of clay or the like, the coating is ordinarily performed by the formation of a pigment film on rollers and then transferred therefrom on to the web A. It should be noted that elements of these diagrams that are common to FIG. 1 are denoted using the same reference symbols.
An additional description with reference to FIG. 1 is given hereinafter. The symbol 4 in FIG. 1 denotes an air turn. The purpose of the air turn 4, which is arranged in a roller part that is readily soiled by the application medium, for example paint, is to improve the quality of the coated surface and prevent stoppage of the machine due to soiling. A high-pressure flotation system is used to non-contactingly alter the movement angle of the web A. The air turn, which has a circular arc-shaped surface, jets air from an air hole provided in its surface to form a film of air between itself and the web A that passes by this surface. The symbol 4c denotes a carrier rope sheave. Although carrier ropes are ordinarily used to carry the web through the dryer part of a paper machine, they may also be used to carry the web through an on-machine coater. A carrier rope includes a group of two ropes that pass along a route identical to the path of the web, the web being carried with the tip-ends of selvedges (strips of thickness of the order of 100 mm that are cut off by a water nozzle of the wire part of the paper machine) formed in the operation side of the web being held between and pulled by said group of ropes. When the carry of the web using these strips is completed the water nozzle is actuated to afford an overall increase in width.
The symbol 5 denotes an infrared dryer that constitutes one type of non-contact dryer. The two surfaces of the web A are dried by a pair of infrared dryers 5 opposingly provided in the downstream side of the air turn 4 about the upward-moving web A. The infrared dryers, who afford the non-contact drying of the web, are of either an electrical or a gas type. The advantage of the gas type over the electrical type lies in its much cheaper running costs. The gas infrared dryer combusts a fuel gas that heats a ceramic emitter to a temperature of 110° C. or above which then emits infrared rays on to the web A.
The symbol 6 denotes a blade coater which constitutes one type of a post-metering style of coater for coating the lower surface of the web A. The coated amount is 5 to 15 g/m2 per surface, and the speed is 1000 to 2000 m/min. The blade coater 6, which includes a backing roll 6a and coater head 6c, sprays an excess amount of application medium, for example paint, upward on to the web A wound around the lower surface of the back up roller 6a, and this is then scraped off and measured (metered) using a steel blade. The scraped-off application medium, for example paint, is re-circulated. The symbol 5a denotes an infrared dryer used to dry the surface coated by the blade coater.
The symbol 7 denotes an air dryer which constitutes one type of non-contact dryer. The web A is non-contactingly conveyed and dried by way of an air jet. The symbols 8 and 10 denote dryer cylinders, the cylinders of larger diameter being heated by a blown-in steam. The symbols 8a and 10a denote canvases that are used to push the web A against the cylinders.
FIG. 3 is an expanded view of the middle section of FIG. 1. In FIG. 3, the size press 3 for coating the two surfaces of the web A and the blade coater 6 for coating the lower surface of the web A are used alternatively. When the size press 3 is used the web A is passed along the path shown by B in the diagram, and when the blade coater 6 is used the web A is passed along the path shown by C in the diagram. As shown in the diagram, along path B the web rises directly up from the air turn 4 passing through the infrared dryers 5 used to dry the two surfaces thereof whereupon, by way of an air turn 4A and paper roller d, it passes air turns 4C, 4D before reaching a furthermost upstream air dryer 7a. While along path C it is guided by a paper roller e from the air turn 4 to pass below the blade coater 6 where its lower surface is coated whereupon, while rising therefrom, it passes an infrared dryer 5a where its coated surface is dried before, passing the air turns 4C, 4D, reaching the furthermost upstream air dryer 7a. It should be noted that, in order to coat the upper surface of the web A, as shown by the path D of FIG. 1, the web A is led below the blade coater 6 by a plurality of paper rollers g whereupon, after rising therefrom, it is moved upstream in the reverse direction to where the upper surface of the web A is coated by the blade coater 6, following which it rises to where the coated surface of the web A is dried by the infrared dryer 5A before, by way of air dryers 7A, 7B, reaching the dryer cylinder 8.
As is described above, in a conventional on-machine coater as shown in FIG. 1 and FIG. 3, the size press 3 and the blade coater 6 for coating the lower surface of the web A are used alternatively, and while the web A passes along the path shown by B in FIG. 3 when the size press 3 is used, the web A passes along the path shown by C in FIG. 1 when the blade cover 6 is used. Because the path B and the path C of the web A are so different, the following problems are inherent thereto. First, because the coated surface of the two surfaces of the web A coated by the size press 3 are dried by the infrared dryers 5 and the coated surface of the lower surface side of the web A coated by the blade coater 6 is dried by the infrared dryer 5a, the equipment costs, maintenance costs and space for the provision thereof are unavoidably replicated. Reviewing the arrangement of the machine it is clear that it should be possible to contrive the path of the web A to facilitate the combined use thereof. Second, a carrier rope must be provided for each of path B and path C of the web A. By way of example, in a design in which two each, making a total of four, is provided in the operation side, interference problems arise between the web-carrying ropes. Although, as another method, the provision thereof in each of the end surface of an operation-side roller and the end surface of a drive-side roller has been considered, there are inherent dangers associated with the provision of a carrier rope in the drive side. Furthermore, although the cutting of the used web-carrying rope and provision of a new web-carrying rope each time the coated part is changed has also been considered, the operation that this involves is troublesome and, in addition, it is difficult from the viewpoint of both the maintenance of the web-carrying ropes and the increased amount of equipment and so on.
What is needed in the art is to facilitate improved web carry and, in addition, to avoid the replication of equipment (non-contact dryer).